<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let num1 = +prompt('1')
        let num2 = +prompt('2')
        let a = prompt('+-*/')
        switch (a) {
          case '+':
            alert(num1+num2)
            break;
                case '-':
            alert(num1-num2)
            break;
          case '*':
            alert(num1*num2)
            break;
          case '/':
            alert(num1/num2)
            break;
         default:
            alert('没有找到')
            break;
    }
    </script>
</body>
</html>